Get some carb cleaner and spray it around all the air pipe joints. If the revs increase then theres your air leak.
To test the throttle switches (there are 2 - one at the top and one hidden)
First check if they both click. The top switch is the wide open throttle switch. The one at the bottom clicks soon as you rev it.
Engine on idle - rev the engine by hand then press the top throttle switch in. The revs should drop. if not then its a wiring or throtle switch fault. Quite common for the switch wires to break.